The present invention relates to a holographic stereogram preparation apparatus capable of three-dimensionally recognizing an actually picked-up image, a computer-generated image, and the like.
A holographic stereogram is prepared as follows. An object is sequentially picked up from different observation points to obtain a number of images. These images, which are used as original images, are recorded sequentially as hologram elements in the form of strips or dots onto a piece of hologram recording medium. When a user looks at this holographic stereogram with only one eye from a certain position, the user discriminates a two-dimensional image as an aggregate of image information of a part of each hologram element. When the user looks at the holographic stereogram from another position shifted from the above-mentioned position, the user discriminates another two-dimensional image as an aggregate of image information of another part of each hologram element. Accordingly, when a user looks at a holographic stereogram with both eyes, a recorded image is recognized as a three-dimensional image.
In general, a holographic stereogram as described above is prepared by a holographic stereogram preparation apparatus 100 as shown in FIG. 1. The holographic stereogram preparation apparatus 100 comprises a laser light source 101 which emits a laser beam L10 having a single wavelength and excellent coherence, a half-mirror 102 which spectrally divides the laser beam L10, into an objective laser beam L11 and a reference laser beam L12, optical parts 103 to 107 and a display device 108 which construct an optical system for the objective laser beam L11, optical parts 109 to 111 which construct an optical system for the reference laser beam L12, a hologram recording medium 112 onto which the objective laser beam L11 and the reference laser beam L12 are converged, and the like.
The optical system for the objective laser beam L11 specifically comprises a total-reflection mirror 103, a first cylindrical lens 104 which diffuses the objective laserbeam L11 in a one-dimensional direction, a collimator lens 105 which parallelizes the diffused objective laser beam L11, a projective lens 106, a second cylindrical lens 107 which guides the objective laser beam L11 to the hologram recording medium 112, all arranged orderly along the optical axis from the input side. The display device 108 is constructed by a transmissible liquid crystal panel and is provided between the collimator lens 105 and the projective lens 106. An image based on image data outputted from an image processing section not shown is displayed on the display device 108.
The optical system for the reference laser beam L12 specifically comprises a cylindrical lens 109 which diffuses the reference laser beam L12 in a one-dimensional direction, a collimator lens 110 which parallelizes the diffused reference laser beam L12, and a total-reflection mirror 111 which reflects the reference laser beam L12 to guide this beam to the hologram recording medium 112. The hologram recording medium 112, for example, is made of a photosensitive film and is fed from a feed reel 113. Also, this medium is intermittently fed in accordance with an image displayed on the display device 108, by a feed mechanism omitted from the figure, and is then wound on a wind reel 114.
The laser beam L10 is emitted from the laser light source 101 and enters into the half-mirror 102. This beam is spectrally divided into an objective laser beam L11 and a reference laser beam L12 by the half-mirror 102. The objective laser beam L11 is let into the display device 108 by the cylindrical lens 104 and the collimator lens 105, and is subjected to image-modulation in accordance with the image displayed when the beam passes through the display device 108. The objective laser beam L11 thus subjected to image-modulation is let into the hologram recording medium 112 through the projective lens 106 and the cylindrical lens 107. Also, the reference laser beam L12 is let into the hologram recording medium 112 through the optical system consisting of the cylindrical lens 109, the collimator lens 110, and the total-reflection mirror 111.
Accordingly, a video displayed on the display device 108 is sequentially exposed and recorded in the form of strips or dots taking interference fringes caused by interference between the objective laser beam L11 subjected to image-modulation and the reference laser beam L12 as hologram elements.
Meanwhile, the holographic stereogram preparation apparatus 100 as described above has a problem that the holographic stereogram is affected if a vibration or the like is applied when each hologram element is exposed and recorded onto the hologram recording medium 112. Specifically, in the holographic stereograin preparation apparatus 100, the state of the interference fringe exposed and recorded becomes unstable, resulting in a phenomenon that the diffraction efficiency or the brightness is lowered at a part of the hologram element recorded and formed, even when a vibration equivalent to the wavelength of the laser beam L or so is applied. Also, if a much greater vibration or the like is applied in the holographic stereogram preparation apparatus 100, there appears a problem that hologram elements are not recorded or formed at all on the hologram recording medium 112.
If a holographic stereogram is recorded with a partial hologram element thereof recorded at a low diffraction efficiency as described above, only the hologram element becomes dark when the holographic stereogram is reproduced, and hence, the uniformness of the image is deteriorated.
Therefore, the holographic stereogram preparation apparatus 100 is additionally provided with an antivibration device which restricts a vibration or the like applied from outside and which quickly damps the applied vibration, in order that stabilized hologram elements are exposed and recorded onto the hologram recording medium 112. The antivibration device is constructed by an air damper a spring, or the like appropriately provided between a substrate mounting respective optical components forming the laser light source 101 and the optical system described above and the apparatus casing.
Meanwhile, in the holographic stereogram preparation apparatus 100, for example, a semniconductor excitation YAG laser, an air-cooled argon gas laser, an air-cooled krypton laser or the like is used as the laser light source 101. In the holographic stereogram preparation apparatus 100, since a laser head section of the laser device described above has a high temperature and makes bad influences on optical components and the like, an air-cooling device is additionally provided to perform cooling. The cooling device cools the laser head section, the heat sink member, and the like of the laser device by ventilation using a cooling fan. Accordingly, it is effective that the cooling device is provided at a position close to the laser device.
However, since the cooling fan of the cooling device rotates and operates during recording of hologram elements onto the hologram recording medium 112, the holographic stereogram preparation apparatus 100 becomes a vibration source so that the holographic stereogram preparation apparatus 100 is kept vibrated. Consequently, the holographic stereogram preparation apparatus 100 has a problem that the anti-vibration apparatus effectively operates with respect to a vibration and the like which are applied from outside but it is difficult to prepare a holographic stereogram with high precision due to influences from a vibration generated by an internal cooling device.
The present invention, hence, has been proposed to provide a holographic stereogram which solves problems of the conventional holographic stereogram preparation apparatus as described above, carries out efficient cooling for its laser device and the like, reduces influences such as vibrations, and enables a highly precise holographic stereogram.
A holographic stereogram preparation apparatus according to the present invention which achieves the above object comprises: an optical system for letting an objective laser beam subjected to image-modulation based on each image of a parallax image sequence and a reference laser beam having coherence with respect to the objective laser beam enter into a recording medium, and for recording interference fringes generated by the objective laser beam and the reference laser beam, as a hologram element, onto the recording medium; anti-vibration means for supporting at least the optical system on a casing while preventing vibrations; and cooling means for cooling at least the optical system. The cooling means is constructed by a drive section whose vibrations are prevented from being transferred to the optical system by providing the cooling means in a side of the casing, and a duct made of a non-rigid material provided between the drive section and the optical system.
In the holographic stereograin preparation apparatus according to the present invention constructed as described above, the optical system is supported by an anti-vibration device while preventing vibrations, and therefore, interference fringes based on an objective laser beam and a reference laser beam are stabilized so that hologram elements are precisely exposed and recorded on a recording medium, even in a case where a vibration or the like is applied from the outside. Also, the holographic stereogram preparation apparatus cools the optical system by the cooling means, and therefore, increase of the temperature inside the apparatus is restricted. Further, in the holographic stereogram preparation apparatus, the cooling means is provided in the casing side, and an anti-vibration means is provided between the casing and the optical system. As a result of this, influences of vibrations generated by the cooling means onto the optical system are restricted so that interference fringes depending on the objective laser beam and the reference laser beam are stabilized. As a result, hologram elements are precisely exposed and recorded on the recording medium. Accordingly, the holographic stereogram preparation apparatus prepares a holographic stereogram of an image quality with high precision, which consists of bright and stable hologram elements having a high diffraction efficiency.
As has been specifically explained above, the holographic stereogram preparation apparatus according to the present invention comprises an anti-vibration support means for supporting at least an optical system on the casing while preventing vibrations and a cooling means for restricting at least the optical system to restrict increase of the temperature inside the apparatus. This cooling means is constructed by a drive section whose vibrations are prevented from being transferred to the optical system by providing this cooling means in the casing side, and a duct made of a non-rigid material provided between the drive section and the optical system. As a result of this, influences on the optical system can be securely restricted not only with respect to vibrations applied from outside but also with respect to internal vibrations generated from the drive section of the cooling means. Accordingly, the holographic stereogram preparation apparatus makes an objective laser beam and a reference laser beam stably enter into a recording medium, so that hologram elements consisting of interference fringes based on the objective and reference laser beams are exposed and recorded on the recording medium with the hologram elements stabilized. A bright holographic stereogram having a high diffraction factor can thus be prepared.